The invention relates to a dispensing valve, and more particularly an aerosol valve which allows delivery of a measured quantity of the aerosol product from a receptacle in which the product is confined.
Such valves are well known, they generally take the form of a double valve. Thus, they comprise a hollow body which is formed from a cylindrical casing of rigid material, closed by a cover which also allows the valve to be fixed to the receptacle and provided with an inlet orifice.
Two seals having fluid-tight joints create a lock chamber inside the valve. A distributor guided at its ends, travels through the center of the valve with a return spring which holds it towards the cover. Formed at the top end of the distributor is a control rod which extends through the cover allowing the distributor to be displaced by means of a head having a push button. The distributor has two series of channels, one set putting the chamber into communication with the liquid in the receptacle when the valve is in its rest position, or when it leaves this position allowing the chamber to be filled, the others opening to the exterior when the button is pressed to allow the contents to be dispensed by the internal pressure or by pumping.
The inlet orifice may have a filling tube if it is desired to use the valve in a higher position above the receptacle. On the other hand, the valve may be placed immediately upstream of the front seal if, to improve precision, it is preferred to use it in a lower position with the receptacle inverted.
Normally, the control rod has an axial discharge duct so that it forms a tube. The control rod and distributor together form an atomizer in which the tube allows the feeding of a spray nozzle mounted on the tube.
Each of the two fluid-tight joints which seal the lock chamber are generally simple sliding joints, flat or having a lip, in which the distributor may slide up and down. However, for the valve to be perfectly fluid-tight in the rest position it is necessary for the joint of the external or rear seal to be made of an elastomer, which may contact the distributor shoulder.
On the other hand, the joint of the internal or front seal does not normally serve any purpose except during operation, that is for a limited time. It does not therefore require such perfect fluid-tightness and as such is sometimes integral with the casing, despite the rigidity of the material used for making the latter.
However, even a small leak through the front seal affects the amount delivered and these valves are often used to deliver products, such as medicines, which are to be dispensed in very small, exact amounts. Moreover, the spring, a member which is not precisely made, may be advantageously placed in an admission chamber upstream of the front seal, rather than in the lock chamber. This configuration is expensive because it may require the presence of undercuts in the distributor to allow fluids to enter the lock chamber. Also, a second, removable joint of elastomer is then used, in spite of its inferior chemical behavior, to permit the seal to flex over the undercut portion.
Often the two seals are immobilised by means of a fluid-tight sleeve formed of a semi-rigid plastic material. The thickness of the sleeve may be varied to modify the internal volume of the lock chamber without the use of a complex and more expensive member.
In particular, FR 2494390 describes a valve with a lower joint of conical shape having a lip and states that the sleeve could be made integral therewith, but with the disadvantage that it is formed of the same, expensive material. While it is true that this allows the number of components to be reduced by one and simplifies mounting at a small increase in the cost of tooling, the advantages obtained do not outweigh the disadvantages mentioned above. Also, the precision of the valve may be adversely affected by use of an elastic sleeve.
In general, the valves in question are filled by intrusion or forced opening, that is the tube is mounted in place on a pump which injects the necessary amount of product in the liquid state, under high pressure. This opens at least one of the seals at the joints to provide a channel to allow the receptacle to fill. The dissymmetry in the joint structure may be utilized to facilitate opening of the seal when it is operated in reverse and subjected to large pressure differences.
Frequently, it is the front joint which is forced open, but if it is not elastic a special arrangement allows a rear joint to operate instead, at least when an auxiliary joint is not used.